/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */

class Solution {
public:
    TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) {
        if (root == nullptr)return nullptr;
        int temp = root->val;
        int x = p->val;
        int y = q->val;
        if (temp == x || temp == y)return root;
        if ((x > temp && y < temp) || (x<temp && y>temp))return root;
        else if (x < temp && y < temp)return lowestCommonAncestor(root->left, p, q);
        else return lowestCommonAncestor(root->right, p, q);
    }
};